Observational Study On The UT-LS Water Vapor, Ozone And Temperature Vertical Distributions Over Tibetan Plateau And Its Adjacent Region

The water vapor, ozone and temperature distributions and variations in the upper troposphere and lower stratosphere (UTLS) over Tibetan Plateau (TP) reflect the stratosphere and troposphere interaction. Their influences on the changes of global climate and environment are of significance. While the accurate vertical distribution data about water vapor, ozone, and temperature data over TP are not sufficient. Confidence in the satellite products exist uncertainties, and they depend on the system analysis results. Based on the observations of tropospheric and stratospheric water vapor, ozone and temperature using balloon-borne Cryogenic Frost point Hygrometer (CFH, n=31), Electrochemical Concentration Cell ozonesonde (ECC, n=71) and radiosonde (RS80\InterMet\RS92=82) over Tengchong (25.0N,98.5°E,1656m) in August 2010, Naqu(31.3°N,92.0°E, 4500m) in August 2011, Lhasa (29.7°N,91.1°E,3650m) during May-July 2012 and Linzhi (29.67°N,94.33 °E,2992 m) during June-July 2014., we degrade the high-resolution sounding profiles by using two methods (the Lagrangian linear interpolation of the fine resolution pressure grid to the MLS retrieval grid, and also, the use of MLS averaging kernels to smooth the sounding data to the MLS grid) to validate MLS water vapor, ozone and temperature data over Tibetan Plateau and its adjacent regions. We also present validation studies of AIRS water vapor, ozone and temperature using the linear interpolation sounding data over Tibetan Plateau and its adjacent regions. MLS water vapor and ozone products are corrected based on the validation results over Tibetan Plateau and its adjacent regions. In addition, we correct the RS92 radiosonde RH measurements by removing the sensor time-lag error, mean calibration bias, and solar radiation error over Dali Yunan, Gaize Tibet, and Litang Sichuan in February, May and July 2008, then we present the intercomparison results between corrected RS92 and MLS, AIRS water vapor measurements. We present the detailed structure of the tropopause transition layer as revealed by balloon sounding observations of temperature, ozone and water vapor over Tibetan Plateau and its adjacent regions, and provide the analysis about the individual profile. The major conclusions include the follow points:1. MLS water vapor products show dry biases relative to CFH measurements above the altitude of 38 hPa and below the altitude of 121 hPa over TP during summer. The comparison results show slight differences using different methods to degrade CFH vertical resolution between 100 hPa and 38 hPa, but MLS water vapor products mostly show wet biases, especially in the vicinity of cold point temperature (100-68 hPa). The mean biases of MLS water vapor increase with increasing pressure. Relative to the corrected RS92 water vapor measurements, MLS water vapor products show dry biases above the altitude of 121 hPa in July, while they show wet biases below the altitude of 121 hPa. The mean bias of AIRS is within below the altitude of 100 hPa. We recommend to use MLS water vapor products between 100-215 hPa relative to CFH, while we recommend to use AIRS water vapor products below and including the altitude of 250 hPa relative to CFH.2. MLS ozone concentrations are markedly higher than that of ECC value over TP in summer, especially at 83 hPa. The vertical distributions of ozone relative difference in Tengchong, Naqu, Lhasa, and Linzhi during the Asia summer monsoon period show similar structures. The mean biases of MLS ozone significiantly increase with increasing pressure. MLS ozone overpass location contributes a lot to the high biases of MLS ozone products. AIRS generally overestimates ozone concentrations.3. MLS v3.3 and v4.2 generally overestimate the temperature. The mean biases of MLS v3.3 are within-2.3±1.5 K above and including the altitudes of 82 hPa and within -3.5K±2.1 K below and including the altitudes of 100 hPa, the corresponding values for MLS v4.2 are within -2.1±0.7 K and -5.7±1.4 K respectively. The mean bias during Asia summer monsoon is larger than it before Asia summer monsoon. In February and March, large changes are existed in the temperature bias profile. In May, AIRS at all pressure levels underestimates the temperature except at 70 hPa and 100 hPa. In July, AIRS show cold bias at all pressure levels except at 100 hPa (1.5±0.6 K). The temperature bias of AIRS is smaller than the temperature bias of MLS.4. The water vapor mean biases are respectively decreased by 10% and 6% in the troposphere and stratosphere after the mathematical statistics of correction. The ozone mean biases do not have obvious decrease above the altitude of 68 hPa (only 1%), while the mean bias at 83 hPa is decreased by 79%, the corresponding decrease in the troposphere is 26%.5. The upper (the cold point tropopause:CPT) and lower (the level of minimum stability:LMS) boundaries of the tropopause transition layer are 17.7 km (390K) and 12.6 km (357.8 K). The CPT potential temperature and altitude averages are approximately 15 K and 1 km higher than the tropical regions. The LMS altitude average shows similar value with the tropical regions, but the LMS potential temperature average show 10 K higher value than it in tropical regions. The upper troposphere was frequently supersaturated with respect to ice after the onset of the Asia summer monsoon. The RHi in this supersaturation layer could reach 140% over Tengchong and Linzhi,160% over Lhasa. The extremely low water vapor values and high ozone values in the middle troposphere were the results of the air parcels transport form mid-latitude stratosphere to the troposphere over Tengchong. The extremely high water vapor values and low ozone values in the vicinity of tropopause are evidence that the air parcel has experienced rapid deep convective ascent from southwest low latitudes.